The present invention relates to pressure valve actuators and more specifically actuators for high pressure gas release.
Pressurized gas springs are commonly used for counter-balancing and supporting loads in It various applications. The amount of force available from the spring is supplied by pressure of the compressible gas inside of the spring where typically a full charge is around 300 psi. Since gas springs are charged to this high pressure they are preset at the manufacturer and not adjustable by the end-user. However, there are some applications where the load cannot be predetermined and adjustability by the end user is desirable.
A known solution is to build in a mechanical means of adjusting the leverage in the mechanical system in which the gas spring is used rather than reducing the gas spring pressure, which has been disregarded as an alternative because of the difficulty in metering the release of a low volume of high pressure gas. However, adding a mechanical structure such as an adjustable lever arm to regulate the net spring force is expensive and adds to the bulk and complexity of the completed assembly. There is therefore a need in the art to provide a means for adjusting the internal working pressure of a gas spring which can be done accurately and repeatably even by an end user having very little skill.
The present invention provides the end-user with a device (hereinafter xe2x80x9cadjustorxe2x80x9d) to adjust the pressure of the gas spring to match their particular-installation. The adjustor includes a unique pressure-release actuator mechanism which regulates the rate of gas discharge to approximately equal bursts small enough to give precise adjustment through application of an inertial force to the gas spring pressure release valve. The actuator causes just one metered burst of released gas regardless of how quickly or slowly it is turned. This mechanism also eliminates the chance of over-bleeding since the size of the burst is not dependent upon the end user""s skill. The adjustor is coupled directly to the end of the gas spring and also provides an attachment point for the spring. Because it is integrated directly into the device, it is compact and does not interfere with other mechanical structures in the surrounding environment.
The operation of the present invention is achieved by the use of an inertial impact element, hereinafter referred to as the xe2x80x9cfiring pin,xe2x80x9d which forceably impacts the stem of the gas spring pressure release valve. According to the invention, a manual rotary actuator spring-loads and releases the firing pin. The actuator includes a simple lever which contacts a flange on the firing pin through a sweep of its arc as it is turned. When the actuating lever contacts the firing pin flange, it first begins retracting the firing pin against the force of a drive spring. As the lever is turned farther, the spring becomes fully loaded. Finally, the firing pin is released as the end of the lever sweeps past the edge of the firing pin flange.
The firing pin is then accelerated forward, impacting the valve stem of the gas spring pressure release valve. As the firing pin impacts the valve stem and rebounds from it, the momentum of the firing pin at impact is sufficient to unseat the gas spring release valve so that a small burst of gas is released, thus reducing the working pressure of the gas spring. This impact/burst process may be repeated by continued turning of the rotary actuator until the pressure in the gas spring is reduced to the point of desired adjustment. With every 360 degree turn of the rotary actuator, the process is replicated regardless of how quickly or precisely the actuator is turned. Hence, small amounts of pressure can be incrementally, and therefore accurately, released by an operator with very little skill.
More specifically, the applicant has invented a gas spring pressure adjustment mechanism which includes an adjustor body attached to a housing of a gas spring. The adjustor body is be positioned adjacent to a gas release valve stem in the body of the gas spring. A firing pin is in slidable engagement with the adjustor body and is moveable between retracted and extended positions. When the firing pin is close to its extended position, it contacts the pressure release valve stem. A spring, acting between the adjustor body and the firing pin, forceably drives the firing pin forward toward its extended position. The firing pin is retracted and then released by a rotary actuator which includes an engagement mechanism that moves the firing pin. The engagement mechanism is preferably a lever which extends radially from an actuator shaft that contacts a flange on the firing pin along a portion of its arc as it is rotated. The invention further includes a unique method of attachment between the adjustor body and the housing of the gas spring that also provides adjustment means for limiting the forward travel of the firing pin. The mounting means comprise an interconnecting collar having male threads which engage threads in aligned bores in both the adjustor body and the gas spring housing. The collar includes an axial bore through which the firing pin travels, and the end of the collar provides a stop means for restricting the forward travel of the firing pin. An axial slot in the collar which, when fully assembled to the gas spring, is aligned with a slot in the top of the adjustor body so that the combined slots provide a cavity through which the actuator engagement means passes as the actuator shaft is turned. To prevent inadvertent or accidental actuation of the adjustor mechanism, the actuator shaft includes a head having tool drive means so that a tool must be used to turn the shaft to operate the invention.
It is therefore the main object of the present invention to provide an easily controlled gas release valve actuator for a gas spring. It is a further object of the invention to provide a gas spring pressure release valve which may be accurately used by an unskilled person. Yet a further object of the present invention is to create a high pressure release valve which is safe to use and is protected against accidental operation.